Gas adjusting valves in the conventional technology are mainly electromagnetic ones which adjust a gas flow in a linear gradient mode. Such an electromagnetic valve uses an electromagnet as a driving element to vary the gas flow by changing a current of a winding of a magnet coil. The current of the magnet coil is substantially in a linear relation with the variation of the gas flow. The electromagnetic valve is usually used in thermostatic control of a gas-typed water heater, and characterized by having a fast adjusting speed and a large operating current. However, the electromagnetic valve will still consume a certain quantity of electric energy when keeping a certain quantity of gas flow. Besides, one electromagnetic valve is able to adjust the gas flow in only one gas channel, and the electromagnetic valve needs a high accuracy and cost during manufacturing.
Among the conventional gas appliances which need automatic adjustment of the gas flow, not all the gas appliances require the gas flow to be adjusted fast, continuously and linearly, however, some of the gas appliances need to vary gas flows in various gas channels simultaneously. To save electric power, the motor operated gas adjusting valve in the gas appliance is required not only to consume no electric power under a predetermined gas flow, but also to be capable of shutting off the gas channel. For example, in a household automatic gas stove, when the stove has a double-ring fire, the adjusting valve for controlling the gas flow in each burner is required to control different gas flows in two gas channels corresponding to the inner-ring fire and the outer-ring fire at the same time, and be capable of shutting off the two gas channels. Similarly, when the stove has a three-ring fire, the gas adjusting valve is required to control the gas flows of three gas channels corresponding to the inner-ring fire, the middle-ring fire and the outer-ring fire at the same time, and be capable of shutting off the three gas channels. In the prior art, each gas channel needs an independent gas adjusting valve; and if an independent shutting off function is needed, an additional gas cut-off valve needs to be disposed in each gas channel when the adjusting valve does not have the gas shutting off function. As a result, more than five gas electromagnetic valves including a main switch valve are needed, even if the stove is only a household gas stove with two burners both having a double-ring fire.
A CN patent application entitled “double closed type gas valve with adjustable flux”, whose publication number is CN1601184, which is incorporated by reference, is published in the Chinese patent gazette. The double-closed type gas adjusting valve therein can only shut off gas channels of a big fire and a kindling/small fire at the same time, rather than shut off the gas channel of the kindling fire or the big fire independently. The gas flow of the kindling fire is only a fixed value and cannot be adjusted independently. Besides, adjusting of the big fire can only be performed in an open-loop control mode because relative positions of an adjusting body and an adjusting opening cannot be accurately determined. When the gas valve is controlled in the open-loop mode, it is hard to control the amount of the flow accurately, and the situation will be worse after multiple times of adjustment. Consequently, in the prior art, there is no such a gas adjusting valve that can control multiple gas flows of gas channels independently at the same time or shut off each gas channel independently.